posted by anony mouse on .
What is the direction of the net magnetic field at the point?
I'll describe the figure here:
Imagine a cartesian plane.
At (0,y) is a wire carrying a current out of the screen.
At (0, -y)is a wire carrying identical current out of the screen.
At (x, 0) is a point -- so the point is equidistant from the two wires.
I'm confused because if I put my right thumb in direction of the current, and fingers curl in direction of the field, the field is a counterclockwise circle around each wire. But how do I know what is the field at the dot? I feel like it can be either up + up = up, or left + right = 0. But I can't tell which?
There is also an option for not enough information.
never mind I got it, I used a compass to figure out the point on the circle to figure out direction
Only the B-field components in the y direction will be additive. The x components will cancel at any (x,0)because of symmetry considerations.
Because of the right-hand rule, the field direction will be +y for x>0 and -y for x<0 (unless I got my hand rules mixed up.)